The synchronous reluctance rotating electrical machine includes a rotor and a stator. The rotor includes a shaft which rotatably pivots and extends axially around a rotating shaft, and a rotor core which is externally fitted to and fixed to the shaft. The stator includes a stator core which is disposed around an outer peripheral portion of the rotor core while being spaced apart from the rotor core and has a plurality of teeth arranged at intervals in a circumferential direction, and a multi-phase armature winding with multiple poles, which is wound on each of the plurality of teeth.
In the rotor core, a plurality of cavity portions for each pole are formed parallel to each other in a radial direction. It is often the case that, in order to conform to a flow of magnetic flux formed when the armature winding is energized, each of the cavity portions is formed to be curved inward in a radial direction, so that a pole center is located innermost in the radial direction.
By forming the cavity portion in this manner, a direction in which it is easy for a magnetic flux to flow and a direction in which it is difficult for the magnetic flux to flow are formed in the rotor core. Also, a synchronous reluctance rotating electrical machine uses the reluctance torque generated by the cavity portions to rotate the shaft.
By the way, it can be expected that a synchronous reluctance rotating electrical machine should be able to be applied in various fields and achieving higher output and reduction in size is required. Accordingly, it is desired to realize a larger capacity and a higher rotation speed for a synchronous reluctance rotating electrical machine. On the other hand, if cavity portions are formed in the rotor core, the rotor core can be deformed easily. For this reason, when a rotor core is rotated at a high speed, there is a likelihood that the rotor core will be deformed by a centrifugal force generated by the high-speed rotation. Thus, there is a case in which deformation of the rotor core is made difficult by increasing the thickness of a portion called a bridge formed between both circumferential ends of a cavity portion and the rotor core, or by forming a structure called a center bridge at a center of a cavity portion in the circumferential direction.
However, if the thickness of a bridge is increased or a center bridge is formed, there are cases in which magnetic saturation of these bridges is prevented. For this reason, it is then difficult to obtain a desired reluctance torque, and there is a likelihood that the torque characteristics of a synchronous reluctance rotating electrical machine will deteriorate.